Methods and systems for heating a wide bandgap substrate

Abstract

Methods and systems of heating a substrate in a vacuum deposition process include a resistive heater having a resistive heating element. Radiative heat emitted from the resistive heating element has a wavelength in a mid-infrared band from 5 μm to 40 μm that corresponds to a phonon absorption band of the substrate. The substrate comprises a wide bandgap semiconducting material and has an uncoated surface and a deposition surface opposite the uncoated surface. The resistive heater and the substrate are positioned in a vacuum deposition chamber. The uncoated surface of the substrate is spaced apart from and faces the resistive heater.

What is claimed is: 
     
         1 . A method of heating a substrate in a vacuum deposition process, the method comprising:
 providing a resistive heater having a resistive heating element, wherein radiative heat emitted from the resistive heating element has a wavelength in a mid-infrared band from 5 μm to 40 μm that corresponds to a phonon absorption band of a substrate, wherein the substrate comprises a wide bandgap (WBG) semiconducting material and has an uncoated surface and a deposition surface opposite the uncoated surface;   positioning the resistive heater and the substrate in a vacuum deposition chamber, wherein the uncoated surface of the substrate is spaced apart from and faces the resistive heater;   operating the vacuum deposition chamber at a pressure less than or equal to 5×10-4 Torr; and   generating the radiative heat from the resistive heating element, wherein the uncoated surface of the substrate is directly heated by absorbing the radiative heat;   wherein the WBG semiconducting material of the substrate comprises Al 2 O 3 , Ga 2 O 3 , SiC, MgO, LaAlO 3 , Gd 3 Ga 5 O 12 , MgF 2 , LiF, MgGa 2 O 4 , or CaF 2 .   
     
     
         2 . The method of  claim 1 , wherein the WBG semiconducting material of the substrate is an oxide and has a bandgap from 3 eV to 9 eV. 
     
     
         3 . The method of  claim 1 , wherein:
 the resistive heater comprises two or more of the resistive heating elements, the two or more of the resistive heating elements being individually controlled and arranged in two or more zones;   the method further comprises providing feedback to the resistive heater with a heating control system, the heating control system comprising a pyrometer having an optical filter that selectively allows optical radiation in the mid-infrared band to pass through; and   the heating control system measures a plurality of temperatures across the deposition surface of the substrate, using the pyrometer, wherein the feedback comprises providing a signal including the plurality of temperatures to the resistive heater, to control the two or more of the resistive heating elements.   
     
     
         4 . The method of  claim 3 , further comprising calibrating the heating control system prior to positioning the substrate in the vacuum deposition chamber, wherein the calibrating comprises:
 placing a calibration platen spaced apart from the resistive heater;   heating the calibration platen with the resistive heater;   measuring a calibration temperature profile of the heated calibration platen; and   determining settings for the resistive heater based on the calibration temperature profile.   
     
     
         5 . The method of  claim 4 , further comprising, after the calibrating:
 replacing the calibration platen with the substrate;   measuring the plurality of temperatures; and   calculating compensation settings for the resistive heater.   
     
     
         6 . The method of  claim 1 , wherein the WBG semiconducting material of the substrate comprises the SiC. 
     
     
         7 . A method of depositing an epitaxial oxide on a substrate in a vacuum deposition process, the method comprising:
 positioning a resistive heater and a substrate in a vacuum deposition chamber, the resistive heater comprising two or more resistive heating elements that are individually controlled and arranged in two or more zones, wherein the substrate comprises a wide bandgap (WBG) semiconducting material and has an uncoated surface and a deposition surface opposite the uncoated surface, wherein the positioning comprises the uncoated surface being spaced apart from and facing the resistive heater;   operating the vacuum deposition chamber at a pressure less than or equal to 5×10 −4  Torr;   generating radiative heat from the resistive heater, wherein the radiative heat has a wavelength in a mid-infrared band of 5 μm to 40 μm that corresponds to a phonon absorption band of the substrate;   providing feedback to the resistive heater with a heating control system, the heating control system comprising a pyrometer having an optical filter that selectively allows optical radiation in the mid-infrared band to pass through; and   depositing an epitaxial oxide layer on the deposition surface of the substrate;   wherein the providing feedback comprises:
 measuring, using the pyrometer, a plurality of temperatures across the deposition surface of the substrate; 
 providing a signal including the plurality of temperatures to the resistive heater, to control the two or more resistive heating elements. 
   
     
     
         8 . The method of  claim 7 , wherein the two or more resistive heating elements comprise SiC. 
     
     
         9 . The method of  claim 8 , wherein the SiC is n-type doped. 
     
     
         10 . The method of  claim 7 , wherein the two or more resistive heating elements comprise Ga 2 O 3 . 
     
     
         11 . The method of  claim 10 , wherein the Ga 2 O 3  is coated with SiC or is n-type doped. 
     
     
         12 . The method of  claim 7 , wherein the WBG semiconducting material of the substrate is an oxide and has a bandgap from 3 eV to 9 eV. 
     
     
         13 . The method of  claim 7 , wherein the WBG semiconducting material of the substrate comprises Al 2 O 3 , Ga 2 O 3 , SiC, MgO, LaAlO 3 , Gd 3 Ga 5 O 12 , MgF 2 , LiF, MgGa 2 O 4 , or CaF 2 . 
     
     
         14 . The method of  claim 7 , further comprising calibrating the heating control system prior to positioning the substrate in the vacuum deposition chamber, wherein the calibrating comprises:
 placing a calibration platen spaced apart from the resistive heater;   heating the calibration platen with the resistive heater;   measuring a calibration temperature profile of the heated calibration platen; and   determining settings for the resistive heater based on the calibration temperature profile.   
     
     
         15 . The method of  claim 14 , further comprising, after the calibrating:
 replacing the calibration platen with the substrate;   measuring the plurality of temperatures; and   calculating compensation settings for the resistive heater.   
     
     
         16 . The method of  claim 7 , wherein the pyrometer further comprises a detector, and the optical filter is configured to selectively allow the optical radiation in a mid-infrared wavelength range of 6 μm to 15 μm to pass through to the detector. 
     
     
         17 . The method of  claim 16 , wherein the detector is a two-dimensional detector array. 
     
     
         18 . The method of  claim 16 , wherein the detector is a broadband detector array that is wavelength-sensitive to the mid-infrared wavelength range of 6 μm to 15 μm. 
     
     
         19 . The method of  claim 16 , wherein the pyrometer further comprises a lens, wherein the lens and the detector are configured to scan the deposition surface of the substrate to measure the plurality of temperatures across the deposition surface of the substrate. 
     
     
         20 . The method of  claim 19 , wherein the measuring the plurality of temperatures comprises tilting the lens and the detector of the pyrometer to scan the deposition surface of the substrate. 
     
     
         21 . The method of  claim 7 , wherein the measuring the plurality of temperatures comprises transmitting the optical radiation emitted from the substrate through a viewport;
 wherein the pyrometer is outside the vacuum deposition chamber, and the viewport is between the deposition surface of the substrate and the pyrometer.